SLAC National Accelerator Laboratory
BL4-2 Biological Small Angle Scattering/Diffraction

Data Acquisition Using Gas Chambers with sup_main

    SUP_MAIN is a data collection program developed by F. Golding and M.H.J. Koch at the European Molecular Biology Laboratory Hamburg Outstation.  This program supports all types of detectors built by A. Gabriel at EMBL-Grenoble: linear, quadrant and 2D detectors.  SSRL BL 4-2 is equipped with a linear detector and a quadrant detector.  The data acquisition system, as it is configured on BL 4-2, can also record simultaneously up to 8 frequency signals (i.e. ion chamber current for data normalization).  There are several channels available on a voltage-to-frequency converter for recording physical quantities that can be converted to voltage.

Run the program

Read in a data collection system parameter file

Set-up the experimental parameters

Set-up the display parameters

Start data collection

Monitor progress of data collection

Save data in the histogram memory on hard disk

Clear the memory content

Data format

Cautionary notes
 

Run the program:

     Log on to the EMBL data collection PC using your SSRL domain account

     Open your folder on the BL4-2 Windows2000 server

     Double-click on the SUP_MAIN icon

     Note: If the SUP_MAIN icon is not in your directory, contact the beamline personnel for help.
 

Read in a data collection system parameter file (unless you use default parameters):

     FILE/OPEN and select the desired file

     FILE/Save As will save the current parameter file
 

Set-up the experimental parameters:

    A.     PARAMETERS/GENERAL VALUES

            super cycle (data will be written on the hard drive every super cycle)

           cycles (a cycle is made up of a set number of individual frames as defined elsewhere)
Note: if data collection is started without clearing the memory, the new frames will be added to the old frames.

           calibration channels (N-1, where N is the total number of the CCU channels, normally N=8).  Please use the default value of 8 at all times.

           result file’s first character (one alphabet character)

           result file’s index (two digit number) which will be incremented automatically

          Note: data file name is XNNMMM.LLL, where X is the first character, NN is the index, MMM is the type of file (000 corresponds to a header file, 001 to the scattering data, 002 to the calibration data), and LLL corresponds to the date.  Data is currently saved on d:\

         starting method (select signal or keyboard)

         display delay (normally set to 0)

         restart method between cycles (select signal, keyboard, or auto)

    B.  PARAMETER/FRAME TIMES and SIGNALS and set-up the following:

         number of frames (number of individual scattering patterns)

         wait and read (exposure) time for each set of frames*

         time unit (use ­ and/or ¯ to change time unit)

         select TTL level/pulses from the time-frame generator (TFG), if desired

         use [insert] to obtain access to a second set of wait/read settings

        *Note: One example would be 10 frames of ‘5 ms wait and 30 s read’, or, stated equivalently, a total of 300s exposure time subdivided into 10 scattering curves.   The exposure time should be shorter when radiation-induced change is a concern.  The 5 ms wait is the shortest time that the electronic modules can handle.  In time-resolved studies you may want multiple wait / read settings in order to follow both fast and slow changes, for example: 20 frames of 5 ms wait / 100ms read, immediately followed by 20 frames of 5 ms wait / 500ms read, and then 10 frames of 5 ms wait / 1s read.
 

Set-up the display parameters:

    DISPLAY/PARAMETERS

    while scanning, you will have the choice of viewing a single plot (whole) or a subdivided one (left, right).  For each (left, right, whole), you can select from the following options:

    off/frame/calibration (use ­ and/or ¯ to change)

    log/linear plot (use ­ and/or ¯ to change)

    plot type (simple plot is normally selected, use ­ and/or ¯ to change)

    which frames to display (leaving this blank will always display the most recent frame)

    1st/last channel to display (1 through 1024 usually corresponds to the total usable length of the detector)

    which calibration channel to display (normally the signal from the ion chamber monitoring the incident flux is connected to CCU channel #0)
 

Start data collection:

    Open the x-ray shutter manually

    START

    There are two options for stopping data collection:

    Stop at cycle end

    Stop immediately
 

Monitor progress of data collection:

    Dfram to display x-ray scattering data (F9)

    Dcal to display calibration channel (F10)

    Dboth to display both (F11)
 

Save data in the histogram memory on hard disk:

    Dump
 

Clear the memory content:

    CLEAR

    Note: One should clear memory before recording a new set of data otherwise the new data will be added on to existing data in the memory.
 

Data format:

    Data can be saved in either binary (standard) or ascii formats.  More extensive information about data format is available in the on-line OTOKO User Manual.
 

Cautionary notes:

    There are some parameters that should never be changed by users, including:

    PARAMETER/DETECTOR PARAMETERS
    PARAMETER/CAMAC address
    AUX/IO